Herein is disclosed fuser members useful in electrostatographic reproducing apparatuses, including digital, image on image, and contact electrostatic printing and copying apparatuses. The present fuser members may be used as fuser members, pressure members, transfuse or transfix members, and the like. In an embodiment, the fuser members comprise an outer layer comprising a polymer and having thereon, a liquid release agent. In embodiments, the release agent is a mercapto-functional release agent. In embodiments, the outer layer of the fuser member comprises nano-size copper metal particles that react with the mercapto functional liquid release agent.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member, and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles and pigment particles, or toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support, which may be the photosensitive member itself, or other support sheet such as plain paper.
The use of thermal energy for fixing toner images onto a support member is well known. To fuse electroscopic toner material onto a support surface permanently by heat, it is usually necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner material cools, solidification of the toner material causes the toner material to be firmly bonded to the support.
Typically, the thermoplastic resin particles are fused to the substrate by heating to a temperature of between about 90° C. to about 200° C. or higher depending upon the softening range of the particular resin used in the toner. It may be undesirable to increase the temperature of the substrate substantially higher than about 250° C., because of the tendency of the substrate to discolor or convert into fire at such elevated temperatures, particularly when the substrate is paper.
Several approaches to thermal fusing of electroscopic toner images have been described. These methods include providing the application of heat and pressure substantially concurrently by various means, a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, a belt member in pressure contact with a heater, and the like. Heat may be applied by heating one or both of the rolls, plate members, or belt members. The fusing of the toner particles takes place when the proper combinations of heat, pressure and contact time are provided. The balancing of these parameters to bring about the fusing of the toner particles is well known in the art, and can be adjusted to suit particular machines or process conditions.
During operation of a fusing system in which heat is applied to cause thermal fusing of the toner particles onto a support, both the toner image and the support are passed through a nip formed between the roll pair, or plate or belt members. The concurrent transfer of heat and the application of pressure in the nip affect the fusing of the toner image onto the support. It is important in the fusing process that no offset of the toner particles from the support to the fuser member takes place during normal operations. Toner particles offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thus increasing the background or interfering with the material being copied there. The referred to “hot offset” occurs when the temperature of the toner is increased to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member. The hot offset temperature or degradation of the hot offset temperature is a measure of the release property of the fuser roll, and accordingly it is desired to provide a fusing surface, which has a low surface energy to provide the necessary release. To ensure and maintain good release properties of the fuser roll, it has become customary to apply release agents to the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, nonfunctional silicone oils or mercapto- or amino-functional silicone oils, to prevent toner offset.
U.S. Pat. No. 4,029,827 discloses the use of polyorganosiloxanes having mercapto functionality as release agents.
U.S. Pat. No. 4,101,686 to Strella et al. and U.S. Pat. No. 4,185,140 also to Strella et al., both disclose polymeric release agents having functional groups such as carboxy, hydroxy, epoxy, amino, isocyanate, thioether, or mercapto groups.
U.S. Pat. No. 4,935,785 to Wildi et al. discloses a process for fusing, wherein copper or copper oxide can be used as a resistive material.
U.S. Pat. No. 5,157,445 to Shoji et al. discloses toner release oil having a functional organopolysiloxane of a certain formula.
U.S. Pat. No. 5,370,931 to Fratangelo et al. discloses a fuser member having a volume graft outer layer having copper oxide dispersed therein.
U.S. Pat. No. 5,395,725 to Bluett et al. discloses a release agent blend composition wherein volatile emissions arising from the fuser release agent oil blend are reduced or eliminated.
U.S. Pat. No. 5,698,320 discloses the use of fluorosilicone polymers for use on fixing rollers with outermost layers of perfluoroalkoxy and tetrafluoroethylene resins.
U.S. Pat. No. 5,716,747 discloses the use of fluorine-containing silicone oils for use on fixing rollers with outermost layers of ethylene tetrafluoride perfluoro alkoxyethylene copolymer, polytetrafluoroethylene and polyfluoroethylenepropylene copolymer.
U.S. Pat. No. 5,729,813 to Eddy et al. discloses a fuser member having an outer fluoroelastomer and alumina layer, the outer layer may further include not more than 30 parts by weight copper oxide.
U.S. Pat. No. 5,933,695 to Henry et al. discloses a rapid wake-up fuser member having an outer release layer, which can contain copper oxide therein.
U.S. Pat. No. 6,183,929 B1 to Chow et al. discloses a release agent comprising (a) an organosiloxane polymer containing amino-substituted or mercapto-substituted organosiloxane polymers, wherein the amino or mercapto functional groups on at least some of the polymer molecules having a degree of functionality of from about 0.2 to about 5 mole percent, and (b) a nonfunctional organosiloxane polymer having a viscosity of from about 100 to about 2,000 centistrokes, and wherein the mixture has a degree of functionality of from about 0.05 to about 0.4 mole percent.
U.S. Pat. No. 6,514,650 to Schlueter et al. discloses an electrostatic component having an outer layer having a perfluoroelastomer and copper oxide.
U.S. Pat. No. 7,291,399 discloses a fuser member having an outer fluoropolymer layer having copper oxide dispersed therein, and a release agent containing both of amino- and mercapto-functionalities.
The use of polymeric release agents having functional groups, which interact with a fuser member to form a thermally stable, renewable self-cleaning layer having good release properties for electroscopic thermoplastic resin toners, is described in U.S. Pat. No. 4,029,827.
Mercapto-functional polydimethylsiloxane fluid is currently used in fuser subsystems as a release agent. The mercapto functional groups bond to fluoroelastomers and other substrates by way of coordination with particulate filler in the release layer material. Copper oxide is the most common example of a filler that provides a suitable bonding site for functional fluids. Lead oxide and zinc oxide are other known examples. While this release mechanism is useful in monochrome xerographic platforms, release layers loaded with conventional fillers do not provide sufficient release for high speed monochrome or color xerographic marking fusers, where toner coverage is higher and oil bonding sites on the surface of the fuser are limited. Amine-functional fluids provide sufficient coverage of the fuser member, but also adhere to paper surfaces, causing many problems in post-fusing operations such as book binding, post fuser adhesion and MICR printing. These post-fusing issues associated with the use of amine-functional fuser fluid make it attractive to use mercapto, or other functional silicone release fluids that do not react with and adhere to paper surfaces. Specifically, 3M Post-It notes are not always able to attach to the resulting paper due to the presence of amino-functional oil on the final copy or print substrate. Adding metal oxides and metal particles has been explored in fusing subsystems in the past, but the sizes of the of these particles have been micron-sized, rather than nano-sized. Therefore, an alternate to amino oil for high speed color fusing would be highly desirable to address fuser life and post fusing issues.
Therefore, it is desired to provide a combination of fuser coating and fusing oil which provides for desired physical properties such as thermal conductivity, and release performance of the resulting fuser topcoat, increases fuser life, and decreases the occurrence of hot offset. It is further desired to provide a combination of functional oil that provides adequate coverage for color xerographic marking and avoids the many post-fuse issues associated with the use of amine-functional fuser fluids. It is also desired to provide a fuser oil system that has adequate coverage for use in high speed monochrome, color and MICR-type electrostatographic apparatuses.